Updated July 04, 2015.
What Are Heat Cramps?
Heat cramps are painful muscles spasms that occur in the arms, legs, or abdomen that usually occur after several hours of exertion in the heat. In addition to muscle cramps, other symptoms of heat cramps may include faintness, dizziness, weakness, and excessive sweating.Usually an athlete suffers from heat cramps after several hours of exertion and excessive sweating that results in dehydration.
What Causes Heat Cramps?
The exact cause of heat cramps is unknown, but the theories most commonly cited include:- Altered neuromuscular control
- Dehydration
- Electrolyte depletion
- Poor conditioning
- Muscle fatigue
- Doing a new activity
Muscle cramps are more common during exercise in the heat because sweat contains fluids as well as electrolyte (salt, potassium, magnesium and calcium). When these nutrients, particularly sodium, fall to certain levels due to excessive sweating, the incidence of heat cramps increase.
Also see: Hyponatremia | Water Intoxication
While all these theories are being studied, researchers are finding more evidence that the "altered neuromuscular control" hypothesis is the principal pathophysiological mechanism the leads to exercise-associated muscle cramping (EAMC). Altered neuromuscular control is often related to muscle fatigue and results in a disruption of muscle coordination and control.
Treating Heat Cramps
As soon as you recognize any of the symptoms of a heat illness, take the following actions:- Stop activity, and sit quietly in a cool place.
- Drink a sports beverage with electrolytes (you can make you own sodium-based solution with 1/4 teaspoon table salt mixed in a quart of water).
- Gently stretch and massage the cramping muscle.
- Hold the joint in a stretched position until the cramp stops.
- Seek medical attention for heat cramps if they do not subside in 1 hour.
Preventing Heat Cramps
Follow these tips to minimize your risk of developing heat cramps:- If you are going to exercise in hot weather, it's important to acclimatize to the heat for about a week before beginning any intense exercise. This allows your body to gradually adapt to the heat.
- Hydrate well before and during exercise and replace lost electrolytes such as sodium, potassium and magnesium with food or a sports drink (drink 16 to 20 oz/hour).
- Avoid exercising during the hottest time of day; train closer to sunrise or sunset.
- Wear light, loose clothing, so sweat can evaporate. Better yet, invest in some clothes that wick moisture from your skin to the outer layer of the clothing where it can evaporate more easily. Brands like CoolMax®, Drymax®, Smartwool or polypropylene all have this property.
- Use sunscreen to prevent sunburn, which can limit the skin's ability to cool itself.
- Wear a hat with a brim.
- If you feel your abilities start to diminish, stop activity and seek out a cool, shaded place.
- Do not drink alcohol or beverages with caffeine before exercise because they increase the rate of dehydration.
- Remember, it is easier to prevent heat illness than to treat it once symptoms develop.
Preventing Muscle Cramps
Until we learn the exact cause of muscle cramps, it will be difficult to say with any confidence how to prevent them. However, these tips are most recommended by experts and athletes alike:- Improve fitness and avoid muscle fatigue
- Stretch regularly after exercise
- Warm up before exercise
- Stretch the calf muscle: In a standing lunge with both feet pointed forward, straighten the rear leg.
- Stretch the hamstring muscle: Sit with one leg folded in and the other straight out, foot upright and toes and ankle relaxed. Lean forward slightly, touch foot of straightened leg. (Repeat with opposite leg.)
- Stretch the quadriceps muscle: While standing, hold top of foot with opposite hand and gently pull heel toward buttocks. (Repeat with opposite leg.)
Most muscle cramps are not serious. If your muscle cramps are severe, frequent, constant or of concern, see your doctor.
Sources:
Cause of Exercise Associated Muscle Cramps (EAMC) — altered neuromuscular control, dehydration or electrolyte depletion? M. P. Schwellnus. British Journal of Sports Medicine 2009; 43:401-408.
Muscle Cramp. The American Orthopaedic Society for Sports Medicine. http://orthoinfo.aaos.org/topic.cfm?topic=A00200.
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